Field
Thermosetting resin compositions are provided that are useful for mounting onto a circuit board semiconductor devices, such as chip size or chip scale packages (“CSPs”), ball grid arrays (“BGAs”), land grid arrays (“LGAs”) and the like (collectively, “subcomponents”), or semiconductor chips. Reaction products of the compositions are controllably reworkable when subjected to appropriate conditions.
Brief Description of Related Technology
The popularity of hand held display devices has made their demand increase dramatically in recent years. Manufacturing throughout has consequently been challenged to increase in order to meet the growing demand. One area that is particularly troublesome for manufacturers is the treatment and handling of defective subcomponents. For instance, during the manufacture of a circuit board subassembly a multitude of semiconductor devices are electrically connected to the board. The board may then be tested to evaluate function. Sometimes the board fails. In such cases, it is desirable to identify the semiconductor device that caused the failure, remove it from the board and reuse the board with the remaining functioning semiconductor devices.
Ordinarily, subcomponents are connected to electrical conductors (or, metallization) on a circuit board by the use of a solder connection. However, when the resulting subassembly is exposed to thermal cycling, vibration, distortion or is dropped, the reliability of the solder connection between the circuit board and the subcomponent(s) often become(s) suspect. After a subcomponent is mounted on a circuit board, the space between the subcomponent and the circuit board is ordinarily filled with a sealant resin (commonly referred to as underfill sealant) in order to relieve stresses caused by thermal cycling, thereby improving heat shock properties and enhancing the reliability of the assembled structure.
However, since thermosetting resin compositions that form cross linked networks when cured are typically used as the underfill sealant, in the event of a failure after the subcomponent is mounted on the circuit board, it is difficult to replace the subcomponent without destroying or scrapping the so-formed subassembly in its entirety.
Notwithstanding the state-of-the-art, it would be desirable for an underfilling sealant to flow rapidly by capillary action in the underfill space between the subcomponent or semiconductor chip and the circuit board; to cure rapidly under low temperature conditions; to provide good productivity and thermal shock resistance, while allowing the substrates with which it is to be used to be readily processed and easily separated from a defective subcomponent or semiconductor chip under conditions that does not compromise the integrity of the remaining subcomponents or semiconductor chips remaining on the substrate or the substrate itself; and to be reworkable in the event of failure of the defective subcomponent or semiconductor chip once assembled onto the circuit board.